Progress of information society is quite remarkable in recent years, and, in addition to wired communication, utilization of wireless communication has been increasing as a communication method in a lot of information communication devices and services. Accordingly, demand for a radio frequency that is a limited resource also has been increasing, and depletion of an assignable frequency has become a major problem in countries around the world. In general, license management of the frequency is performed by the government, and only those whom licenses are assigned are allowed to utilize the frequency, under strict management, in a specific place and time. However, to meet the frequency demand that is considered to continue to increase in the future, a new frequency utilization method is demanded that is not restricted by a conventional utilization method.
Therefore, in recent years, as the new frequency utilization method to solve the depletion problem of the frequency, a method has been studied for utilizing a frequency band (white space) that is not used spatially and temporally in spite of being assigned already. For example, research and development, and standardization have been performed, such as a cognitive radio communication system in which a user who is not licensed (hereinafter referred to as “secondary user”) utilizes a radio wave in the white space flexibly while avoiding sufficiently influence (interference) on frequency use of an existing system of a user who is licensed (hereinafter referred to as “primary user”) (for example, Non Patent Literature 1).
For example, in a wide area wireless communication system utilizing the white space that is standardized in IEEE 802.22, each wireless station acquires a transmittable channel list (operable channel list) and maximum allowable transmit power based on location information of the station itself, by accessing a white space database (DB) on an IP network. The operable channel list is collectively managed while being updated as required, by a spectrum manager (SM) in abase station (BS) that is a master device. The BS, based on the operable channel list and maximum transmittable power information of each channel, determines a channel capable of maximizing quality of a communication service of the station itself from the operable channel list as an operation channel (channel used for communication), and performs communication at a frequency of the operation channel with a slave station installed in each house and a terminal station such as a mobile phone (CPE: Customer Premises Equipment) in a service range (cell) of the BS.
In addition, the CPE is also capable of acquiring an operable channel list and maximum transmittable power of itself. Due to the fact that the CPE that is a slave device acquires information by performing information acquisition request to the SM of the BS, influence on channel use of the primary user is avoided, and simultaneously, communication of the secondary user is achieved.
In addition, since DB information (utilization condition, such as the operable channel list, maximum transmittable power) is updated constantly depending on a state of use of the primary user, the wireless communication system utilizing the white space, such as IEEE 802.22, includes a function of updating the DE information by periodic DE access or information notification (push transmission) from the DB and achieving maximization of the communication service of itself while switching the operation channel to avoid influence on the primary user.
Incidentally, in addition to the DB access, in accordance with information obtained from a resource manager (RM) for performing notification of channel operable information considering influence (interference) between the secondary users, not only on the primary user, the BS and the CPE are also capable of determining the operable channel and the maximum transmittable power. As a result, it is also possible to further increase frequency utilization efficiency.
Various techniques have been devised relating to the wireless communication system utilizing the white space.
For example, in Patent Literature 1, it is disclosed that, for a method and apparatus in which a specific station operates as an AP station in a WEAN, the specific station operating as a non-AP station that is allowed to operate in an available channel that is not used by a license device, a specific protocol is defined having each information ID including a registration request and a registration response in association with registration of a location of the station for operating in the white space, and the station is able to register a geographical location of itself with an RLS using the registration request and the registration response defined, and to operate as the AP station in the WS.